Cloning and cold-resistance analyses of CfICE1 gene in Cryptomeria fortunei

Cryptomeria fortunei is a conifer species that can attain a height of ~70 m and is cultivated for its timber as well as its ornamental value. It is a subtropical plant that prefers a warm and humid environment. Therefore, low temperature (LT) affects its growth, development, productivity and ecological distribution. Inducer of C-repeat binding factor (CBF) expression 1 (ICE1) plays an important role in the response to cold/freezing stress in plants through the CBF regulation pathway. To date, there is no research on homologue of ICE1 in C. fortunei. In this study, we first isolated the CfICE1 transcript from C. fortunei. The CfICE1 coding sequence was 1728 nucleotides encoding a 575-aa protein and contained a serine-rich motif, a basic helix-loop-helix-Zipper (bHLH-Zip), an ACT domain and a nuclear localization signal (NLS), which were conserved in ICE1 homologous genes. Phylogenetic analysis showed that CfICE1 and all dicots ICE1 proteins were clustered together. CfICE1 had transcriptional activity in yeast cells, was predominantly located in the nucleus and highly expressed in tender needles and roots. 35S::CfICE1 transgenic Arabidopsis thaliana could increase antioxidant enzyme activities and photosynthesis and reduce the malondialdehyde content compared to the wild-type to better cope with LT. Under LT, CfICE1 expression was higher; the C. fortunei clone with stronger cold resistance (CR) significantly upregulated the expression of CfICE1 compared to the weaker clone. In conclusion, these results suggest that CfICE1 plays an active role in CR, which provides a theoretical basis for breeding for CR in C. fortunei.